To install OS X Mountain Lion, download the Mountain Lion installer from the App Store (MacOS X 10.6.8 or higher) and use Unibeast to create a USB installation disk. Once the disk is created, you can then boot from the flash drive to install Mountain Lion! At the boot prompt, be sure to boot verbose using the '-v' option and also set 'GraphicsEnabler=No' as at the time of writing this guide, the NVIDIA GTX 675M cannot be used as the primary GPU and the Intel HD 4000 will need some tweaks later to get QE/CI. Once in the installer, you will need to choose where to install OS X Mountain Lion. You can install to your existing disk on a separate partition or install to a secondary disk (recommended). You will need to make sure that the hard drive you are installing ML to is using the GUID partitioning map and not MBR. If you need MBR, you'll need to patch the installer.

Postinstall

Multibeast

Wifi

The MSI GT70 0ND-202US comes stock with an Intel Centrino Wireless-N 2330 mini PCI Express card which will need to be subbed out with another compatible card. Swapping cards is fairly simple. All you need to do is pop up the speaker panel and disconnect the existing card and replace with the new one. One thing that you must do is make sure the Wifi LED is lit, otherwise, you won't be able to use the card. Here's a complete guide on how to choose an appropriate replacement card and how to get it working: http://www.tonymacx86.com/network/58146-guide-airport-half-mini-pcie.html

Intel HD 4000 QE/CI

Using the MacBook Pro 9,1 SMBIOS, LegacyAGPM.kext, 1920x1080x32, and DSDT injection for 01660004 you can achieve QE/CI. It should also be noted that I have removed AppleIntelSNBFramebuffer.kext as it is not needed with the Intel HD 4000 (probably could stop the kext from loading with DSDT later). Here's the DSDT patch for injecting the ig-platform-id:

Using DSDT Editor, you'll have to apply the above patch as well as the DTGP patch from the patches directory.

Sound

VoodooHDA 2.7.2 - note, you'll have to edit the Info.plist in VoodooHDA.kext so that there isn't a hissing sound coming from the VoodooHDA prefpane.

USB 3.0 fix (temporary)

One thing that I have found is that if you remove AppleUSBXHCI.kext from the plugins in IOUSBFamily.kext, it will treat USB 3.0 ports as just USB 2.0 ports and crashing no longer happens. This is a temporary fix until full USB 3.0 support exists (possibly in a later update). Make a backup of your existing IOUSBFamily.kext and then do the edits and re-install using Kextbeast.

Kexts

Here's the voodoo kexts that I use for my laptop. Included is a kext for the battery, audio, and trackpad (multitouch).